1. Field of the Invention
This invention relates to spot blocked ribbed laminates of thermoplastic films, to the method of making them, and to bags and sacks formed with them.
2. Description of the Prior Art
In U.S. Pat. No. 3,530,023, there is described laminated cellulosic sheet material made by securing together at least two layers of cellulosic fiber sheet material at a plurality of spaced points. These laminates are permanently sealed together at the points and are characterized by being flexible. The laminates of this invention are blocked together not sealed, at the points of attachment and, by the inclusion of embossed ribs, have increased stiffness.
The laminates of this invention differ from quilted laminates, such as described in U.S. Pat. No. 3,466,212, in that it does not have entrapped air pockets, because they have no continuous crisscrossing seal lines. Accordingly, it is much stiffer, because there are no lines in which bending can take place and it has far greater tear resistance, because the layers are free to tear separately.